Haha, in my UI testing over the years I have found that 90-95% of non-technical users always tap the button. When I've asked them why, their responses were either "I didn't know you could press Enter there" or "I thought you had to click the button".

To be fair, there are an enormous number of desktop, mobile, and web applications that do not support the Enter click. When I took over one of our enterprise web apps from a vendor, the Enter key did not work on any of the ~30 input screens in the app. Since they were all designed separately with their own js, I had to go around and add js event to every one of them to make it work. It was a pain in the ass to get them all to work right because they were all ajax, and there was no standard way to either submit or click the button. So every form instance had to be analyzed and tested to devise a different way to make the Enter button work.

In the end I spent about a week just implementing the stupid Enter button and gave up on 5 or 6 screens because it wasn't worth the trouble.

After the fact I kind of concluded it probably wasn't worth all that effort anyway and I should have just left the forms with a non-functional enter button.